1. Field of the Invention
The invention relates to a system manager for a computer system, and, more particularly, to a protocol for asynchronous data transfers between a remote or out-of-band local system manager facility and the system manager.
2. Description of Related Art
The desire to share computer resources has motivated the development and continuing improvement of computer networks. One such computer network is generally referred to as a local area network (or "LAN"). A LAN is a system of computer hardware and software that links components such as computers, printers and other peripherals into a network suitable for transmission between various ones of the linked components located in relative proximity to each other, for example in different offices in a building, or in different buildings situated near one another. Similar to a LAN is a wide area network (or "WAN"). A WAN differs from a LAN in that a telephone network is also required to link at least some of the components included in the network to the remainder of the network components.
Various types of network operating systems are in existence today. They include the NetWare system manufactured by Novell, Inc. of Provo, Utah, the VINES system manufactured by Banyan, and the LAN Manager system manufactured by Microsoft Corporation of Redmond, Wash. While such network operating systems often include a network manager, the network manager included in such systems have typically relies upon the network operating system to provide data to the network manager for performing network management functions. Since network managers have been forced to rely upon data transmitted by the network, prior network managers have focussed on analyzing the health of the network and have not been particularly well suited to analyze the health of the components of the network.
Thus, of the five functional areas of network management (configuration, fault analysis, accounting, performance and security) recognized by the OSI/Network Management Forum, network managers have been best equipped to performing configuration and security management. Network managers can also provide limited fault analysis, but, in most cases, only after failure has occurred. Recently, the development of larger networks, both LAN and WAN, which include multiple printer, communication, database, and file server locations have been contemplated. This drive towards combining increasing numbers of computer components into a single network, has led to an increased demand for greater management capabilities. While, in the past, failure alerts may have been satisfactory, there is an increasing demand for information that will lead to failure whereby potential failures may be reported in sufficient time to allow for corrective action before an actual failure occurs. In addition to this increased demand for information that will lead to failure, the capability of real-time analysis of the performance of a computer system is also seen as a highly desirable management capability, particularly in the development of larger, multiple file server networks which will challenge minicomputers and mainframes for larger scale applications. Furthermore, as many of such networks will utilize a WAN configuration, the need to be able to manage the network from a remote or out-of-band local system facility is of increased importance. Total reliance on local management capabilities would be a significant detriment to such systems since at least one major component of the systems would likely be remotely located with respect to the remainder of the system, thereby producing a network unable to manage the entire system from a single management console or facility.
To provide flexibility in system configuration, it would often be desirable to provide for a remote or out-of-band local system manager facility to control the system manager board. To provide this capability to manage the network from a remote or out-of-band local system facility, an asynchronous communication link between the system manager and the system facility will be required. In order to achieve such a link, a common set of conventions (or "protocol") for communications between the two must be provided. Furthermore, in view of the complex communications anticipated during facility control of the system manager, the asynchronous protocol utilized therewith must enjoy considerable flexibility in use.
The framework used to configure most protocols such as the asynchronous protocol disclosed herein has been established by the International Standards Organizations (or "ISO") and referred to as the ISO model for Open Systems Interconnection (or "OSI"). This model identifies seven (7) distinct levels, or layers, of functional requirements pertaining to a data communications network. Each layer (i) performs a related subset of the functions required to communicate with another system; (ii) relies on the next lower layer to perform more primitive functions and to conceal the details of those functions; and (iii) provides services for the next higher layer.
The OSI layers consist of (1) the physical layer which governs the physical interface between devices and the rules by which bits are passed from one to another; (2) the data link layer which attempts to make the physical link reliable, i.e. error-free, and provides the means to activate, maintain and deactivate the link; (3) the network layer which is responsible for establishing, maintaining, and terminating connections across an intervening communications facility; (4) the transport layer which insures that data units are delivered error-free, in sequence and without losses or duplications; (5) the session layer which provides means for two application processes to establish and use a connection, called a session; (6) the presentation layer which resolves differences in the syntax (representation) of the data exchanged between application entities and provides for the selection and subsequent modification of the syntax to be used; and (7) the application layer which contains management functions and other useful mechanisms to support distributed applications.
The OSI layers are defined so that changes in one layer do not require changes in the other layers. Communication is achieved by having corresponding or "peer" entities in the same layer in two different systems communicate via a protocol. A protocol is a set of rules governing a time sequence of events that take place between peer entities; that is, between equipment or layers on the same level.
The most common way in which protocols are realized is with the use of a header. When a first application has data to send to a second application, the transfers those data to an application entity in the application layer. A header is appended to the data that contains the required information for the peer entity. The original data, plus the header, is now passed as a unit to the presentation layer. The presentation entity treats the whole unit as data, and appends its owns header. This process continues down through the link layer, which generally adds both a header and a trailer. This link layer unit, called a frame, is then passed by the physical layer onto the transmission medium. When the frame is received by the target system, the reverse process occurs. As the data ascends, each layer strips off the outermost header, acts on the protocol information contained therein, and passes the remainder up to the next layer.